Astronomers using telescopes for research purposes are dependent, at least for gathering visible light images, upon having a clear moonless night. Although little can be done about moonlight, astronomers have generally constructed telescopes in locations that have historically large numbers of clear cloudless nights. Nevertheless, when cloud cover does appear, it is important for the astronomer to obtain an objective indication as to the magnitude and extent of the cloud cover.
Astronomers have traditionally monitored cloud cover visually. On a moonlit night, an on-site astronomer can visually ascertain the extent of the cloud cover. However, visual monitoring of cloud cover is difficult under moonless night conditions, particularly when the cloud cover is comprised of thin high cirrus clouds that are nearly impossible to detect visually at night. Ironically, it is these moonless dark nights that are the most desirable for conducting astronomical research in the visible light spectrum.
Additionally, it is not unusual for astronomers to be controlling the telescope from a remote area, such as from a research laboratory thousands of miles away from the telescope. In this case, obviously it is impossible for the astronomer to ascertain the degree of cloud cover present over the telescope. Although at large research telescopes, a telescope assistant is available to provide information on cloud cover, this communication is a poor substitute for an objective cloud image that can be analyzed by the astronomer.
One prior art method of monitoring cloud cover are sensitive video cameras operating in the thermal infrared spectrum. Unfortunately, commercially available cameras have relatively narrow fields of view as limited by the fixed camera lens, are not intended for continuous operation, and are often times prohibitively expensive.